Process for igniting hydrocarbon materials within a subterranean formation

ABSTRACT

A method for igniting hydrocarbons contained in a subterranean formation for in situ combustion operations by passing into the formation a conjunct polymer derived from hydrocarbon processing and having an iodine number greater than 130 and an oxidant into contact therewith.

United States Patent lnventors PROCESS FOR IGNITING HYDROCARBON MATERIALS WITHIN A SUBTERRANEAN FORMATION 4 Claims, No Drawings US. Cl 166/260 Int. Cl E21b 43/24 Field of Search 166/260,

References Cited UNITED STATES PATENTS Bednarski et al.

Monroe Staples et al. Dean Holmes Klein et al....

Hardy et a1. Cornelius et a1 Primary Examiner-Stephen J. Novosad Attorney-Young and Quigg 166/260 166/300X 166/260 l66/300X 166/260 166/260 166/300X 166/260 ABSTRACT: A method for igniting hydrocarbons contained in a subterranean formation for in situ combustion operations by passing into the formation a conjunct polymer derived from hydrocarbon processing and having an iodine number greater than 130 and an oxidant into contact therewith.

PROCESS FOR IGNITING I-IYDROCARBON MATERIALS WITHIN A SUBTERRANEAN FORMATION This invention relates to the production of hydrocarbons from a subterranean formation. 1n another aspect, this invention relates to a method for igniting combustible materials within a subterranean formation in the production of hydrocarbons by means of in situ combustion.

In in situ combustion operations for the production of hydrocarbons, various methods are known for igniting oil, oil residue, tarring substances, and other hydrocarbon materials present in the formation. To this end, highly heated gases are usually introduced into a well bore and forced into an adjacent hydrocarbon-containing formation. It has also been proposed to ignite the in-place hydrocarbons by means of an electric current or thermite bombs. It is, however, difficult to obtain a uniform combustion of the in-place hydrocarbons by these heretofore utilized methods. Furthermore, there is considerable risk of decreasing the permeability with deposits of solid combustion products. Natural drying oils, i.e., triglycerides of unsaturated fatty acids, alcohols, cracked distillates and other oxidizable materials have also been injected into the formation to be therefor contacted with oxidants for spontaneously combusting the in-place hydrocarbons. These heretofore used oxidizable materials often form hardened film within the formation thereby decreasing the permeability and restricting the flow of oxygen to the fire front with resultant inefficiency of the in situ operation. Power requirements for injecting sufficient oxygen to the formation to produce autoignition are also high for heretofore utilized oxidizable materials owing to their relatively low oxidation rates.

It is therefore an object of this invention to provide an improved method for producing hydrocarbons by in situ combustion. Another object of this invention is to provide an improved method for igniting combustible materials within a subterranean formation in the production of hydrocarbons by in situ combustion. Yet another object of this invention is to provide an improved method using an oxidizable material with higher oxidation rates than the oxidizable materials heretofore associated with in situ combustion operations. A further object of this invention is to provide a method for igniting subterranean hydrocarbons that requires less power and causes less plugging of the formation.

According to the invention, the combustible material (oil, oil residue, tar, etc.) in a hydrocarbon subterranean formation is brought to the high temperature required for combustion by introducing into a well and contacting the hydrocarbon containing formation therein a fluid that oxidizes relatively easy, followed by an oxidant having an oxygen volume sufficient. Under the operating conditions the oxidant reacts spontaneously with the oxidizable material.

It is preferred that the oxidizable material be forced into the formation, by diesel oil or an inert gas for example, in order that the spontaneous combustion takes place within the formation where the hydrocarbons for fuel and those to be recovered are positioned. By forcing the oxidizable material and oxidant into the formation spaced from the well bore and bringing said materials together in the formation, wellbore and easing damage as a result of the heat created by the reaction and spontaneous combustion is decreased.

The rate at which the oxidizable material consumes oxygen is relative to the amount of power, labor, and expenditure of oxidant that is required to ignite the formation hydrocarbons. Oxidizable materials having higher oxygen consumption rates also assist in promoting a more uniform burn around the well bore thereby increasing the efficiency of the in situ combustion operation. The oxidizable material utilized in the method of this invention is selected from a group of materials that have improved oxygen consumption rates relative to oxidizable materials previously used for autoignition in in situ combustion operations. The preferred oxidizable materials for use with this invention are conjunct polymers derived from hydrocarbon processing and which have iodine numbers greater than 130. Similar materials as described above but which characteristically have iodine numbers less than are found not to consume oxygen at a satisfactory rate, thereby resulting in waste of power equipment, labor and often resulting in erratic ignition of the formation hydrocarbons.

Examples of the oxidizable materials that can be used in this invention are conjunct polymers having an iodine number greater than about 130 that are formed by acid catalyzed polymerization of hydrocarbons, acid catalyzed alkylation of hydrocarbons, acid catalyzed isomerization of of hydrocarbons, such as for example, a conjunct polymer formed from hydrofluoric acid catalyzed alkylation of isoparaffins in gasoline manufacturing, and aluminum trichloride sludge from diisopropyl synthesis and the like.

In some cases where the iodine number of the oxidizable material is extremely high, these oxidizable materials can be mixed with inexpensive extenders such as glyceride oils. The resultant oxidizable material mixture for this invention should not, however, have an iodine number below 130.

An example of of the method of this invention is as follows:

280 Gallons of a hydrofluoric acid catalyzed alkylation of isoparaffins in gasoline manufacturing, as more completely described in Table I, is injected downwardlythrough the well followed by a slug of 21 gallons of diesel fuel to move the volume of acid soluble oil a distance into the formation of about 1 foot from the well bore. Oxygen is thereafter injected into the formation at the rate of 10 s.c.f./hr.-ft. until ignition occurs at 400 F. Upon ignition, the ignitable slug of acid soluble oil is consumed by ignition and subsequent in situ combustion.

TABLE I ANALYSES OF HF ACID SOLUBLE OILS Proton Distribution by NMR, 72

Aromatic 1.6 Allylic or Benzylic 26.1 Saturated 72.3

"Grams bromine consumed by 100 grams of oil.

Grams iodine consumed by 100 grams ofoil (ASTM-D1959-61). "Milligrams maleic anhydride consumed by one gram of oil. ASTM Method D1644-59.

A detailed study of conjunct polymers that can be used in the method of this invention can be found in Journal of Chemical and Engineering Data, Vol. 8, No. 1 (1963), pp. -160, Miron and Lee.

Other modifications and alterations of this invention will become apparent to those skilled in the art from the foregoing discussion and example, and it should be understood that this invention is not to be unduly limited thereto.

What I claim is:

1. In the production of hydrocarbons by the means of in situ combustion of combustible hydrocarbon material present in a subterranean formation. an improved method of igniting said combustible material, comprising:

injecting an oxidizable material into the hydrocarbon-containing formation, said oxidizable material being a conjunct hydrocarbon polymer having an iodine number greater than 130; and

injecting an oxidant into the adjacent hydrocarbon-containing formation and into contact with the previously injected oxidizable material positioned therein, said oxidant having an oxygen content sufficient to spontaneously react at formation conditions with said oxidizable material to raise the temperature within the subterranean formation to the ignition point of the combustible hydrocarbon material of said formation.

2. A method, as set forth in claim 1, wherein the oxidizable material is a conjunct polymer formed by acid-catalyzed polymerization of hydrocarbons.

3. A method, as set forth in claim 1, wherein the oxidizable material is a conjunct polymer formed by acid-catalyzed alkylation of hydrocarbons.

4. A method, as set forth in claim 1, wherein the oxidizable material is a conjunct polymer formed by acid-catalyzed isomerization of hydrocarbons. 

2. A method, as set forth in claim 1, wherein the oxidizable material is a conjunct polymer formed by acid-catalyzed polymerization of hydrocarbons.
 3. A method, as set forth in claim 1, wherein the oxidizable material is a conjunct polymer formed by acid-catalyzed alkylation of hydrocarbons.
 4. A method, as set forth in claim 1, wherein the oxidizable material is a conjunct polymer formed by acid-catalyzed isomerization of hydrocarbons. 